Plants exposed to adverse environmental conditions develop molecular mechanisms of adaptation and/or defense, the osmoprotectors, which function as compatible solutes and contribute to tolerance via prevention systems and protection against cellular damage caused by these abiotic stresses. This study aimed to identify and characterize the osmoprotectors proline and trehalose in cowpea plants cv. Carijo under controlled conditions of water-deficit and heat stress based on the IPCC scenario of 4.8 degrees C increase in temperature, evaluating their structure and function through computational methods, as well as gene expression by RT-qPCR. The experimental assays were carried out in growth chambers under controlled conditions with different levels of soil water availability, phenological phases and temperature regimes. From the in silico analyses, ten TPS genes and one P5CR gene were identified in Vigna unguiculata, and these were named according to their chromosomal location. The VuP5CR and VuTPS genes play roles in hormone pathway signaling and in the response to light and biotic and abiotic stresses. The genes P5CR (proline) and alpha TPS6 (trehalose) were induced with increased temperature and lower water availability in the vegetative phase of cowpeas. In addition, P5CR also showed induction with 50% water availability at high temperatures. In the pod filling phase, the P5CR and alpha TPS6 genes were repressed with water availability of 75%, while only the P5CR gene was induced when water availability was reduced to 25% under heat stress. P5CR and TPS6 genes were induced in cowpea cv. Carijo in response to associated abiotic stresses (water-deficit and high temperatures), which suggests their participation in the mechanisms of adaptation of the species in adverse environmental conditions.

Arbuscular mycorrhizal fungi (AMF) could establish symbiosis with plant roots, which enhances plant resistance to various stresses, including drought stress and salt stress. Besides AMF, chemical stimulants such as trehalose (Tre) can also play an important role in helping plants alleviate damage of adversity. However, the mechanism of the effect of AMF combined with chemicals on plant stress resistance is unclear. The objective of this study was to explore the synergistic effects of Claroideoglomus etunicatum AMF and exogenous Tre on the antioxidant system, osmoregulation, and resistance-protective substance in plants in response to salt stress. Tomato seedlings were inoculated with Claroideoglomus etunicatum and combined with exogenous Tre in a greenhouse aseptic soil cultivation experiment. We measured the arbuscular mycorrhizal symbiont development, organic matter content, and antioxidant enzyme activity in tomato seedlings. Both AMF and Tre improved the synthesis of chlorophyll content in tomato seedlings; regulated the osmotic substance including soluble sugars, soluble protein, and proline of plants; and increased the activity of superoxide dismutase, peroxidase, and catalase. The combination of AMF and Tre also reduced the accumulation of malondialdehyde and alleviated the damage of harmful substances to plant cells in tomato seedlings. We studied the effects of AMF combined with extraneous Tre on salt tolerance in tomato seedlings, and the results showed that the synergistic treatment of AMF and Tre was more efficient than the effects of AMF inoculation or Tre spraying separately by regulating host substance synthesis, osmosis, and antioxidant enzymes. Our results indicated that the synergistic effects of AMF and Tre increased the plant adaptability against salt damage by enhancing cell osmotic protection and cell antioxidant capacity.IMPORTANCEAMF improve the plant adaptability to salt resistance by increasing mineral absorption and reducing the damage of saline soil. Trehalose plays an important role in plant response to salt damage by regulating osmotic pressure. Together, the use of AMF and trehalose in tomato seedlings proved efficient in regulating host substance synthesis, osmosis, and antioxidant enzymes. These synergistic effects significantly improved seedling adaptability to salt stress by enhancing cell osmotic protection and cell antioxidant capacity, ultimately reducing losses to crops grown on land where salinization has occurred. AMF improve the plant adaptability to salt resistance by increasing mineral absorption and reducing the damage of saline soil. Trehalose plays an important role in plant response to salt damage by regulating osmotic pressure. Together, the use of AMF and trehalose in tomato seedlings proved efficient in regulating host substance synthesis, osmosis, and antioxidant enzymes. These synergistic effects significantly improved seedling adaptability to salt stress by enhancing cell osmotic protection and cell antioxidant capacity, ultimately reducing losses to crops grown on land where salinization has occurred.